1. Technical Field of the Invention
The present invention relates to stators for electric rotating machines that are used in, for example, motor vehicles as electric motors and electric generators.
2. Description of the Related Art
Conventionally, there are known stators for electric rotating machines which include a hollow cylindrical stator core and a stator coil mounted on the stator core.
The stator core has a plurality of slots that are formed in the radially inner surface of the stator core and spaced in the circumferential direction of the stator core. The stator coil is formed by joining a plurality of electric wires. Each of the electric wires includes a plurality of in-slot portions, each of which is received in a corresponding one of the slots of the stator core, and a plurality of turn portions each of which connects an adjacent pair of the in-slot portions and is located outside the slots of the stator core.
Moreover, each corresponding pair of the electric wires forming the stator coil may be joined together by, for example, a method disclosed in Japanese Patent Application Publication No. 2009-219343. According to the method, for each corresponding pair of the electric wires, one of the electric wires has an end portion led out from the radially inner periphery of one slot of the stator core, while the other electric wire has an end portion led out from the radially outer periphery of another slot of the stator core. The end portions of the electric wires are joined together at a position above a coil end part of the stator coil which is located outside the slots of the stator core.
Furthermore, each of the electric wires forming the stator coil is generally comprised of an electric conductor and an insulating coat that covers the outer surface of the electric conductor. In joining each corresponding pair of the electric wires, the insulating coats are first stripped from both the end portions of the electric wires. Then, the stripped end portions of the electric wires are welded together, forming a joint (i.e., weld) therebetween. Thereafter, an insulating material (e.g., a powder resin) is applied to form an insulating layer that covers both the stripped end portions of the electric wires.
However, the thus-formed insulating layer is weaker than the insulating coats of the electric wires which are formed on the electric conductors in the manufacture of the electric wires; therefore, it is easier for the insulating layer to be peeled off from the electric wires than the insulating coats.
Consequently, referring to FIG. 21, when the joint 50B between the electric wires 50A interferes with the inner surface of a housing 10 of the electric rotating machine after mounting the stator in the housing 10, the insulating layer 50C may become peeled off from the joint 50B, resulting in an insulation failure of the joint 50B.